EUROCODE 1, PART 1.7 ACCIDENTAL ACTIONS …

1 - 1 - EUROCODE 1, PART ACCIDENTAL ACTIONS background document first DRAFT January 2005 by A. Vrouwenvelder U. Stieffel G. Harding - 2 - NOTATIONS 3 0. INTRODUCTION 4 1. GENERAL 5 2. ACCIDENTAL ACTIONS 5 DEFINITION OF ACCIDENTAL ACTIONS 5 ACCIDENTAL VERSUS VARIABLE ACTIONS 5 REPRESENTATION OF ACCIDENTAL ACTIONS 6 3.

2 DESIGN FOR ACCIDENTAL ACTIONS 8 GENERAL 8 DESIGN FOR UNIDENTIFIED ACCIDENTAL LOADS (Robustness) 11 DESIGN FOR IDENTIFIED ACCIDENTAL LOADS 14 4. IMPACT 15 BASICS OF IMPACT ANALYSIS 17 IMPACT FROM VEHICLES 20 IMPACT FROM RAIL TRAFFIC 30 SHIP COLLISIONS

3 31 5. EXPLOSIONS 37 NATURE OF THE action 37 MODEL FOR THE UNCONFINED EXPLOSION 39 LOADS MODELS FOR GAS EXPLOSION PRESSURES IN BUILDINGS 41 DESIGN EXAMPLE OF A COLUMN IN A BUILDING FOR AN EXPLOSION 49 GAS AND FUEL / AIR EXPLOSIONS IN ROAD AND RAIL TUNNELS 53 DUST EXPLOSIONS IN ROOMS AND SILOS 55 REFERENCES 60 - 3.

4 NOTATIONS F = force Fco = compression strength of colliding object Fcs = compression strength of the structure N = number of fatalities per year Pa = probability of not avoiding a collision, given a ship on collision course Pc = probability of collision Pf = probability of failure P(d|f) = probability of a person being killed, given structural failure T = period of time under consideration, mostly a year a = deceleration b = typical dimension of structural object d = distance from structure to the road fs(y) = ship or aircraft position perpendicular to the direction of distribution of initial propagation k = stiffness m = mass of colliding object n = number of cars, ships, per time unit passing a certain point (traffic intensity)

5 Pi = pressure due to explosion r = distance t = time uf = deformation at fracture vo = initial velocity of colliding object vr = velocity of colliding object at impact x,y = coordinates = angle between rod direction and car direction s = FORM influence factor = reliability index (x) = probability rate of a ship getting out of control or a car leaving the road per unit distance = arctan (d/x) dyn = dynamic amplification factor = normal distribution = venting parameter - 4 - 1.

6 INTRODUCTION This background document provides explanatory material in support of the draft of EUROCODE 1, Part , ACCIDENTAL ACTIONS , dated September, 2004. The document is intended for a better understanding of the numbers and rules given in the code. It is envisaged to be of help in setting up National Annexes in the various member states, in applying the document for the design of new structures and for formulating corrections and future improvements. Since the design philosophy for ACCIDENTAL ACTIONS differs from the design philosophy for permanent and variable ACTIONS , it has been unavoidable to include design principles to a limited extent.

7 It should be noted, however, that later on it should be considered if certain parts ought to be transferred from EN 1991-Part to EN 1990. The present version of this background document is a revision of the background document for the ENV. - 5 - 2. ACCIDENTAL ACTIONS Definition of ACCIDENTAL ACTIONS ACCIDENTAL ACTIONS in the EUROCODE system are defined as ACTIONS with low probability, severe consequences of failure and usually of short duration.

8 Typical examples are fire, explosion, earthquake, impact, floods, avalanches, landslides, and so on Next to these identified ACCIDENTAL ACTIONS , structural members may got damaged for a variety of less identifiable reasons like human errors in design and construction, improper use, exposure to aggressive agencies, failure of equipment, terrorist attacks and so on. In the EUROCODE system, fire and earthquake are dealt with in specific parts. The document EN 1991-1-7 deals primarily with impact and explosion. In addition, the document also gives general guidelines how to deal with identified and unidentified ACCIDENTAL ACTIONS in general.

9 Because of the nature of ACCIDENTAL loads the design approach may be different from normal loads. Local damage may be acceptable and non-structural measures ( sprinkler installations or vent openings) may prove to be more cost effective than structural ones. The scope of EN 1991-1-7 gives no attention to events, which are generally denoted as accidents, like persons falling through windows or roofs. The reason is that they have no damaging potential for the structural system. ACCIDENTAL versus variable ACTIONS Figure shows the typical difference between a variable and an ACCIDENTAL load as far as the time characteristics are concerned.

10 The variable load is nearly always present, although its value may be small for a substantial part of the time. However, serious non-zero values will in most cases (wind, snow, traffic) occur many times during the design life of the structure. A typical ACCIDENTAL load, on the other hand, will most probably not occur during the working life of the structure. If the load is present, it normally will take only a short time, varying from a few seconds (explosions) to some days (floods). Figure shows a typical probability distribution for the one year maximum of the loads.